Study of laser scattering effect on bubbles in the ocean

Abstract

In ocean there are two kinds of bubbles according to mechanism of bubble generation. One case is bubble existing on the ocean surface and in the upper ocean due to breaking wave phenomena. The radius of bubbles changes from 10 micrometer to 1000 micrometer. Another one is for warship the bubbles varying size from 10 micrometer to 100 micrometer[1,2]. For later mechanism of bubble generation is due to change of a propeller's tip vortex flow field and interaction between cavitation and explosion bubbles. Assuming that the shape of bubble is spherical, Mie scattering model is used to analyze and calculate the behaviors of forward scattering and backscattering of bubble, such as the change of the normalized scattering amplitude intensity with bubble diameter, scattering angle, polarization direction, and laser wavelength. However, with increasing of the size of bubble and particularly while the bubble size is much bigger than that of incident laser wavelength we find the backscattering of bubbles approaches to zero using Mie scattering theory. Apparently, this is no agreement to experimental results. In this paper, the corresponding geometry optics scattering model including the size and shape of bubble is given, the forward scattering and backscattering are analyzed and calculated using the model. Finally, it can be seen that for geometry model there is good agreement to Mie scattering model while the size of bubble approaches to laser wavelength.